The Immunologic Monitoring Laboratory (lML) is a shared facility responsible for serial monitoring of immunologic functions in patients with cancer, who are treated with biologic therapies and participate in clinical trials or research protocols at the UPCI. The IML makes available to its users a broad range of state-of-the-art immunologic assays, performed under a rigorous quality control program. In addition, as advances in immunobiology occur and new assays are requested by the users, the IML performs pre-clinical evaluations of the assays, and when they become reliable and standardized, adds them to the available assay list. Advice to users about test selection and result interpretation is also an important part of the IML's responsibilities. The main categories of assays include phenotypic markers by flow cytometry (35% of total usage); assays measuring effects of anti-cancer vaccines, including antigen-specific T-cell frequency analysis by ELISPOT, tetramer analysis or cytokine flow cytometry (25%); cytokine determinations (20%); cell-mediated cytotoxicity (10%) and apoptosis assays (5%). The IML is operated as a good laboratory practice (GLP) facility. It maintains extensive quality control (QC) and quality assurance (QA) programs, to ensure the validity of test results. It performs over 30,000 assays annually and currently provides scrvices to 32 clinical or research studies, and 85% of its usage is cancer-related. The IML has established a fee-for-service schedule and gives priority as well as discounted fees to the UPCI members. High quality and reproducibility of the assays performed for the UPCI programs contribute to the overall excellence of clinical and research studies.